<template>
    <div id="zoom">
        <img v-lazy="goodsImg"/>
        <div class="event"  @mousemove="handler"></div>
        <div class="big">
            <img v-lazy="goodsImg" ref="big" />
        </div>
        <div class="mask" ref="mask"></div>
    </div>
</template>

<script>
export default {
    methods: {
        handler(event) {
            let mask = this.$refs.mask;
            let big = this.$refs.big;
            let left = event.offsetX - mask.offsetWidth / 2;
            let top = event.offsetY - mask.offsetHeight / 2;

            if (left < 0) {
                left = 0;
            } else if (left > event.target.offsetWidth - mask.offsetWidth) {
                left = event.target.offsetWidth - mask.offsetWidth;
            }

            if (top < 0) {
                top = 0;
            } else if (top > event.target.offsetHeight - mask.offsetHeight) {
                top = event.target.offsetHeight - mask.offsetHeight;
            }

            mask.style.left = left + "px";
            mask.style.top = top + "px";


            big.style.left = -2 * left + "px";
            big.style.top = -2 * top + "px";
        },
    },
    props:["goodsImg"]
};
</script>

<style lang="less" scoped>
#zoom {
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;
    position: relative;

    img {
        /*图片高度自适应*/
        width: 100%;
        height: 100%;
    }

    .event {
        width: 100%;
        height: 100%;
        position: absolute;
        top: 0;
        left: 0;
        z-index: 998;
    }

    .big {
        width: 100%;
        height: 100%;
        position: absolute;
        top: -1px;
        left: 100%;
        border: 1px solid #aaa;
        overflow: hidden;
        z-index: 998;
        display: none;
        background: white;

        img {
            width: 200%;
            max-width: 200%;
            height: 200%;
            position: absolute;
            left: 0;
            top: 0;
        }
    }

    .mask {
        position: absolute;
        width: 50%;
        height: 50%;
        background-color: rgba(0, 255, 0, 0.3);
        position: absolute;
        left: 0;
        top: 0;
        display: none;
    }

    .event:hover ~ .mask,
    .event:hover ~ .big {
        display: block;
    }
}
</style>